Threat Advisory

Signed software abused to deploy antivirus-killing scripts

Threat: Malware Campaign
Targeted Region: Global
Targeted Sector: Technology & IT
Criticality: High
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EXECUTIVE SUMMARY:

A malware campaign leveraging legitimate, signed software to distribute malicious payloads, demonstrating an increasingly sophisticated abuse of trusted digital ecosystems. Threat actors utilized digitally signed applications—typically considered safe by security controls—to bypass detection mechanisms and gain initial footholds on targeted systems. By exploiting the inherent trust associated with signed binaries, the attackers were able to execute code without triggering conventional security alerts, thereby increasing the success rate of infection. The campaign affected a significant number of endpoints globally, indicating a coordinated and well-orchestrated operation rather than isolated incidents. This approach reflects a growing trend where adversaries blend malicious intent with legitimate tools to evade detection and prolong persistence within compromised environments. The primary objective appears to focus on disabling endpoint protection mechanisms, particularly antivirus solutions, to create a permissive environment for further malicious activities such as data exfiltration or secondary payload deployment.[/subscribe_to_unlock_form]

EXECUTIVE SUMMARY:

A malware campaign leveraging legitimate, signed software to distribute malicious payloads, demonstrating an increasingly sophisticated abuse of trusted digital ecosystems. Threat actors utilized digitally signed applications—typically considered safe by security controls—to bypass detection mechanisms and gain initial footholds on targeted systems. By exploiting the inherent trust associated with signed binaries, the attackers were able to execute code without triggering conventional security alerts, thereby increasing the success rate of infection. The campaign affected a significant number of endpoints globally, indicating a coordinated and well-orchestrated operation rather than isolated incidents. This approach reflects a growing trend where adversaries blend malicious intent with legitimate tools to evade detection and prolong persistence within compromised environments. The primary objective appears to focus on disabling endpoint protection mechanisms, particularly antivirus solutions, to create a permissive environment for further malicious activities such as data exfiltration or secondary payload deployment.[emaillocker id="1283"]

The attack chain begins with the deployment of a signed application, often categorized as adware or a seemingly benign utility, which acts as the initial delivery vector. Once installed, the software leverages its update mechanism or embedded functionality to fetch additional payloads from remote servers. These payloads are typically delivered via scripts or installer packages, including PowerShell commands and MSI files, which execute with elevated privileges. A key component of the attack involves disabling antivirus and endpoint security tools through carefully crafted scripts that manipulate system configurations, terminate security processes, or alter registry settings. This defense evasion technique ensures that subsequent malicious actions proceed without interference. The attackers exploit system-level permissions granted to the signed software, enabling deeper system access and persistence. In some observed cases, the campaign may also facilitate the deployment of follow-on malware such as information stealers or remote access tools.

In conclusion, this malware campaign exemplifies the evolving tactics of threat actors who increasingly rely on trusted software and legitimate mechanisms to execute malicious operations. By abusing signed applications, the attackers effectively circumvent signature-based detection and exploit gaps in trust-based security models. The campaign’s emphasis on disabling antivirus solutions highlights a strategic focus on weakening defensive capabilities before executing further malicious objectives. This not only increases the dwell time of the attackers but also amplifies the potential impact on affected systems. Organizations must recognize that code signing alone does not guarantee software safety and should implement layered security approaches, including behavioral analysis, application control policies, and continuous monitoring of system activities. Additionally, restricting the execution of unnecessary software and closely monitoring update mechanisms can reduce exposure to such threats.

THREAT PROFILE:

Tactic Technique ID Technique Sub-Technique
Initial Access T1195.002 Supply Chain Compromise Compromise Software Supply Chain
Execution T1059.001 Command and Scripting Interpreter PowerShell
Persistence T1547.001 Boot or Logon Autostart Execution Registry Run Keys / Startup Folder
Privilege Escalation T1548.002 Abuse Elevation Control Mechanism Bypass User Account Control
Defense Evasion T1562.001 Impair Defenses Disable or Modify Security Tools
T1218.010 System Binary Proxy Execution Regsvr32
T1036.005 Masquerading Match Legitimate Name or Location
Command and Control T1105 Ingress Tool Transfer -

MBC MAPPING:

Objective Behaviour ID Behaviour
Defense Evasion F0004 Disable or Evade Security Tools
F0004 AMSI Bypass
Execution E1059 Command and Scripting Interpreter
Persistence F0012 Registry Run Keys / Startup Folder
Discovery B0013 Analysis Tool Discovery
Command and Control B0030 C2 Communication

REFERENCES:

The following reports contain further technical details:

https://www.bleepingcomputer.com/news/security/signed-software-abused-to-deploy-antivirus-killing-scripts/

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